Aluminum alloy



Patented Sept. 5, 1944 ALUMINUM ALLOY Walter Bonsack, South Euclid,Ohio, assignor to The National Smelting Company, Cleveland, Ohio, acorporation of Ohio No Drawing. Application January 18, 1941, Serial N0.375,043

6 Claims.

This invention relates to alloys, and more par-.

er exposure to prolonged high temperatures, are

especially desirable for the manufacture of castings, such as pistons orother parts, for use in internal combustion engines and the like,

Aluminum-silicon alloys containing suitable amounts of manganese andmagnesium have been used in the production of pistons and the like, Inthese alloys, as the proportion of silicon is increased, the thermalexpansion of the alloy is decreased, and the hardness and wearresistance of the alloy are increased. Their Wear resistance, however,has not been as great as usually desired and the expansion has not beenlow enough. This is because it has usually been necessary to have thepercentage of silicon less than about as higher amounts of silicon havedecreased the machinability and fatigue resistance of the alloyto asubstantial degree.

It is an object of the present invention to provide a castable aluminumalloy having greater hardness, improved wear resistance and goodmachinability.

It is a further object of the invention to provide a machinable alloyhaving improved wear resistance, relatively high strength and fatigueresistance, and a relatively low thermal expansion, and which willretain these properties when exposed to relatively high temperatures,such as those encountered in the operation of internal combustionengines.

In my prior application, Serial No. 366,453, filed November 20, 1940, ofwhich this application is a continuation-in-part, is disclosed analuminum base alloy containing silicon, magnesium, manganese, iron andcopper,

It ,has now been found that the above objects may be accomplished to agreater extent by an aluminum base alloy containing about 18% to 35%silicon, about .1% to 1% magnesium, about 1% to 5% copper, about .6% or.7% to 2% iron, and proper proportions of any two or more hardeningmetals of the group consisting of maganese,

nickel, chromium, cobalt, titanium, columbium,

molybdenum, tungsten, vanadium, zirconium, cerium, tantalum and boron ina total amount of .5% to 5%.

Silicon, which aside from aluminum is the predominant alloyingingredient, may be present in the alloy within the limits of 18% to 35%;but, silicon is preferably present in an amount from about 20% to 30% ofthe alloy. Silicon increases the hardness and wear resistance of thealloy and decreases its thermal expansion. Without suitable quantitiesofthe other above mentioned constituents, however, it has a tendency tocrystallize into relatively large crystals and to decrease themachinability of the alloy,

Iron tends to harden the alloy, decreases its thermal'expansion,increases its machinability, and aids in maintaining the properties ofthe alloy at relativelyhigh temperatures. ably present within theamounts of about 1% to 1.5%, although an alloy having very desirableproperties may be obtained with 2% or so, and with as little as about.6% or .7 iron. Iron like silicon, however, has the property of tendingto crystallize into relatively large crystals in the ab sence ofhardening metals of the groups set out above.

The members of the above group each tend to harden the alloy, decreaseits-thermal expansion and increase its machinability. They are alsobeneficial in that they tend to maintain the desirable properties atrelatively high temperatures, such as those encountered in internalcombustion engines and the like,

Of the metals of the above group, manganese, nickel, cobalt and chromiumare usually most desirable for the reason that they are more readilyavailable and are more easily alloyed with the aluminum, These fourelements function in aluminum alloys as hardeners and have relatively nofunction as grain-refiners.

The remaining hardening metals of the group, namely columbium,molybdenum, tungsten, vanadium, zirconium, cerium, titanium, tantalumand boron are generally recognized as being both hardeners and grainrefiners in aluminum alloys.

of the following elements: about 2% to 1% manganese; about .2% to 1.5%nickel; about .1% to .5% chromium; about .1% to .5% cobalt; about .01%to 25% columbium; about .1% to .5%

molybdenum; about .1% to .5% tungsten; about .1% to .5% vanadium; about.01% to 25% zir- It is preferconium; about .01% to .25% cerium; about.05% to .3% titanium; about .1% to .3% tantalum; and about .005% to .l%boron.

Since each of these hardening metals may tend to crystallize in somewhatdifierent shapes, finer crystals and more desirable properties may beobtained in alloys havinga large number of these metals present, each inrelatively smaller amounts than in alloys having the same totaleffective amount of a lesser number of these metals. Thus, when each ofthe above ten members of the group is present in an amount such asone-fifth of its maximum range'above enumerated, somewhat more desirableproperties are obtained than .1 when two of the element are present inamounts used to obtain substantially th same properties in the alloy aswhen a smaller amount of iron is present.

Th total quantity of the hardening metals in the above group should beless than and should be present in an amount of about .5% or more, andpreferably 1% or more of the alloy. In the preferred alloys havingmanganese, chromium and nickel, with one of the grain refiners 1 andhardening group, such as titanium, present, the preferred amount ofmanganese is about .'7%; the preferred amount of nickel is around 1%;the preferred amount of chromium is around .2%;

and the preferred amount of titanium is about Magnesium, as well asimproving the hardness and tensile strength of aluminum-silicon alloys,increases the elastic properties of the alloy and also improves themachinability, and is preferably present in amounts of about 13% toabout .8%, although as much as 1%, or even somewhat more, may be used,and an appreciable effect is obtained with as little as about .l%.

Copper is beneficial in the alloy in that it aids in increasing itsfatigue strength and further improves its machinability. The preferredamount of copper is 1.5% to 2.5%, but-the desirable properties of thealloy are obtained when copper is present from about 1% to about 5%.

Example I Alloys especially desirable for making pistons preferablycontain: 20% to 30% silicon; .3% to .8% magnesium; 1.5% to 2.5% copper;about 1% to 1.5% iron; about .7% to 1% manganese; around 1% or 1.5%nickel; about 2% chromium; and .l% to 2% titanium. If desired, part ofthe titanium may be substituted by a small amount of tantalum or boron,which also act as grain refiners.

Such an alloy may be readily machined with tools now available; it hasrelatively low expansion; it is relatively hard; and it has relativelygreat wear resistance. It also has comparatively high heat conductivity,excel-lent fatigue strength and elastic properties, and maintains was17.35 10 these over long exposures at high temperatures,

Example II A piston alloy containing 1.8% copper, 4% magnesium, 23%silicon, .8% iron, .5% manganese, .5% nickel and .05% titanium was chillcast into test bars, which were heat treated for twelve hours at 355 F.The tensile strength of the test bars was between 31,200 and 33,900lbs/sq, in; the Brinell hardness was between and and the coeflicient ofthermal expansion This alloy had excellent fatigue strength and elasticproperties, had relatively great wear resistance and maintaineddesirable properties at relatively high temperatures.

The alloys of the present invention are particularly desirable for theproduction of castings, and the castings are susceptible to the usualheat treatments and have tensile strengths and hardnesses substantiallyimproved thereby.

Furthermore, it is to be understood that various modifications of thealloys disclosed herein can be made without departing from my inventionas denfied in the appended claims.

What I claim is:

1. An aluminum base alloy having a relatively low coefficient of thermalexpansion and relatively great wear resistance, containing about 18% to35% silicon, about .l% to 1% magnesium, about 1% to 5% copper, about.'7% to 2% iron, and about .5% to 5% of at least two hardening metalsselected from the group consisting of about .2% to 1% manganese, about.2% to 1.5% nickel, about .l% to .5% chromium, about .l% to .5% cobalt,about .1% to .5% molybdenum, about .1% to .5% tungsten, about to .5%vanadium, about .01 to .25% columbium, about 01% to .25% zirconium,about .0l% to .25% cerium, about 05% to .3% titanium, about .1% to .3%tantalum, and about 005% to .l% boron, with the balance substantiallyall aluminum and minor impurities.

2. An aluminum base alloy having a relatively low coefiicient of thermalexpansion and relatively great war resistance, containing about 20% to30% silicon, about .3% to 1% magnesium, about 1.5% to 2.5% copper, about.'7% to 1.5% iron, and about 1% to 5% of at least two hardening metalsselected from the group consisting of about .2% to 1% manganese, about2% to 1.5% nickel, about .l% to .5% chromium, about .1% to .5% cobalt,about .1% to .5% molybdenum, about .1% to .5% tungsten, about .1% to .5%vanadium, about .01% to .25% columbium, about .01% to .25% zirconium,about 01% to .25% cerium, about 05% to .3% titanium, about .1% to .3%tantalum, and about .005% to .l%. boron, with the balance substantiallyall aluminum and minor impurities.

3. An aluminum base alloy having a relatively lected from the groupconsisting of about .2% to 1% manganese, about .2% to 1.5% nickel, about.1% to .5% chromium, about .1% to .5% cobalt, about .1% to .5%molybdenum, about .1% to .5% tungsten, about .1% to .5% vanadium, about.01% to .25% columbium, about .01% to .25% zirconium, about .01% to .25%cerium, about .05% to .3% titanium, about .1% to .3% tantalum, and about.005% to .1% boron, with the balance substantially all aluminum andminor impurities.

4. An aluminum base alloy having a relatively low coemcient of thermalexpansion and relatively great wear resistance, containing abouttantalum,and about .'005% to .1% boron, with the balance substantiallyall aluminum and minor impurities.

5. An aluminum base alloy having a relatively low coefiicient of thermalexpansion and relatively great wear resistance, containing about 20% tosilicon, about .1% to 1% magnesium, about 1% to 5% copper, about .7 to2% iron, and about .5% to 5% of at least two hardening metals selectedfrom the group consisting of about 2% to 1% manganese, about .2% to 1.5%nickel, about .1% to .3% chromium, and about .1% to .5% cobalt, with thebalance substantially all aluminum and minor impurities.

6. An aluminum base alloy having a relatively low coefficient of thermalexpansion and relatively great wear resistance, containing about 20% to35% silicon, about .1% to 1% magnesium, about 1% to 5% copper, about .7%to 2% iron, about .2% to 1% manganese, about .2% to 1.5% nickel, andabout .05% to .3% titanium, with the balance substantially all aluminumand minor impurities.

WALTER BONSACK.

